Just hours before Amazon's second Prime Day sales event, a self-invented holiday that offers exclusive deals for members of its subscription service, Wal-Mart is eliminating the $50 minimum spending requirement for shoppers to receive free shipping on their online orders.

Also Monday, the discount retailer said it has slashed prices on a handful of products, including a Samsung 55-inch 4K TV for $598. That's half the usual price.

The deals are in addition to a promotion Wal-Mart launched at the end of June, when it started offering a free 30-day trial for ShippingPass, its answer to Prime. The annual subscription service gives shoppers free unlimited two-day shipping for $49, compared with $99 for a Prime membership. However, Prime comes with additional perks, such as video streaming.

Wal-Mart said the number of daily sign-ups for ShippingPass have more than quadrupled since it announced the free trial last week. The subscription service launched as a pilot last May, but until recently, shoppers were put on a waiting list before they could join.

Wal-Mart's swipe at Amazon's day of deals is similar to the approach it took last year, when it reduced the minimum spending requirement for free shipping to $35.

Yet as Amazon has gotten more aggressive with the number of deals tied Prime Day, including rolling out discounts in the week leading up to the July 12 event, Wal-Mart has looked to sweeten its offers as well. But one of its main talking points remains that shoppers can get discounts on its site more than one day a year.

"The online rollbacks will be extended offers beyond just a single day," spokesman Ravi Jariwala said.

The company would not specify exactly how long its new price cuts would last. But in the past, Wal-Mart has said its rollbacks typically last 90 days. The retailer also has not yet decided how long it will offer its free 30-day ShippingPass trial, Jariwala said.

Wal-Mart's promotion for free shipping with no minimum purchase runs through Friday.